Classified ads is an online advertising technique which you can see in hardcore media channels like newspapers for which you have pay high rates.
Online Classified ads are almost free for any type of advertisement on the internet. Some of the websites provide different versions of premium accounts where you can add photos, multiple website links, email address to showcase to visitors
Classified Submission is off page SEO technique Classifieds are techniques for on-line promotion of our brands, products, and services.
If you are interested to learn SEO, check out this SEO Training Course by Intellipaat.
Also, watch this SEO Tutorial to get started with SEO: